You're in a really great position with your Mum on your side. It means you have back-up, and financial and emotional support. You should have a talk with your Mum about wanting to come out to the rest of your family and prepare her to support you if things go south, and be prepared yourself to take any potential clashes. Don't go in with a completely negative expectation of how it's going to go though, you don't know that the worse possible conclusion will occur. You should start with the people you think have the most potential to not have a problem with it and slowly make your way up to the people who you expect the worse from. If at any point you don't want to go any further (come out to people who are more likely to not agree), then you don't have to, you can stop and just be proud with your achievements so far. Coming out can be a grueling process, but unfortunately it's something we have to do in our heteronormative society. But it shows us how strong we are because it takes a lot of courage, and any steps you take, even just the coming out to your Mum, you should be damn proud of yourself. You could even ask your Mum to bring it up with other family members if you don't think you could do it. You need to remember that you are perfectly okay. There's nothing wrong with you. It's this outdated concept that everyone must be heterosexual that's wrong. It can be very hard to deal with and it's absolutely disgusting that we have to deal with it. I hope this helps, beautiful. I hope all goes well.
